The invention relates to a modular transmission unit, in particular a multistage transmission.
Transmission devices in the form of power split drives in the form of superimposed gears are known in a number of embodiments. The following documents are examples:
1. EP 1333194
2. DE 197 55 612 A1
The embodiment in accordance with document DE 197 55 612 A1 comprises a gearbox input shaft, a continuously variable transmission gear coupled with the gearbox input shaft and with the gearbox output shaft that has an input and an output, whereby the input is attached to the gearbox input shaft in a torque-transmitting manner, a fixed transmission stage as well as a superimposed gear with a first input shaft, which is attached in a torque-transmitting manner with the output of the continuously variable transmission gear. Furthermore, a second input shaft is provided, which can alternatively be connected to the gearbox input shaft by means of a first clutch via the fixed transmission stage and an output shaft, which is coupled in a torque-transmitting manner with the gearbox input shaft. The fixed transmission stage is hereby coupled in a torque-transmitting manner on the pinion end with the gearbox input shaft and, in terms of the fixed transmission stage on the drive side, the first clutch is arranged such that it alternatively connects the second input shaft of the superimposed gear on the drive side with the fixed transmission gear. With this solution, it is possible to easily make available a reliable multistage transmission. This solution offers the advantage that, in a multistage transmission with a so-called geared-neutral area created through the combination of a continuously variable transmission gear and a superimposed gear, high engagement speeds are avoided in the area of the first clutch, since it is attached to a spot after the corresponding transmission of the high revolution speed of the drive shaft to the low revolution speed through the fixed transmission stage. This reduces the wear and tear and increases the life span of the first clutch. An important advantage exists however in the direct coupling between the continuously variable transmission, also called CVT, and the transmission input and thus the drive shaft. The continuously variable transmission is thus always coupled with revolutions of the drive machine. An offloading of the superimposed gear in an area of higher revolutions per minute of the output shaft or lower transmission ratios of the continuously variable transmission gear is realized in that a second clutch is provided, which alternatively connects the first input shaft with the output shaft of the transmission gear. This creates a rigid connection between the output shaft of the continuously variable transmission gear and the output shaft, whereby the superimposed gear in the torque flow is bridged. Another important problem of the transfer of power over the continuously variable transmission gear is that it can only transfer a maximum permissible torque due to corresponding dimensioning; otherwise, impermissible slip states are to be observed in the case of very high stress levels, which lead to increased wear of the traction mechanism. However, due to the direct coupling of the continuously variable transmission at the box input, it is always exposed to these provided conditions. That is, the input of the CVT is supplied with the revolution speed at the box input and thus the main engine.
A multistage transmission is also known from document WO 94/15121. It comprises a continuously variable transmission in the form of a traction mechanism box as well as two triple-shaft planetary wheel sets, which are combined into a four-shaft planetary wheel set. The coupling of the individual shafts with the continuously variable transmission also occurs via connecting gears here.
A modular transmission unit is known from document EP 1333194 that was modified with respect to its design such that the loading of the traction mechanism box was considerably reduced and thus the transferability of higher power output, in particular higher power output than with DE 19755612 A1, was able to be ensured via its use. In this embodiment, the modular transmission unit is also designed as a superimposed gear unit. This comprises a box input and a box output, as well as two superimposed gears arranged and coupled together between the box input and the box output. Each of the two transmission gears is thereby designed as a three-shaft planetary wheel. Both are coupled together with each other into a four-shaft planetary wheel. A continuously variable transmission in the form of a traction mechanism box is interposed between the first superimposed gear and the second superimposed gear. Each planetary wheel comprises a sun wheel, a hollow wheel, plant wheels and a spacer. The individual shafts are thereby formed by the sun wheel, the hollow wheel or the spacer of the respective superimposed gear. The box input is connected in a torque-transmitting manner with a first shaft of the first superimposed gear and a first shaft of the second superimposed gear. The box output is connected in a torque-transmitting manner with a second shaft of the second superimposed gear and a second shaft of the second superimposed gear. The two three-shaft planetary wheels are coupled into a four-shaft planetary wheel through the coupling of the first and second shafts of the first and second superimposed gears. The continuously variable transmission in the form of a traction mechanism box is arranged between the third shaft of the first and second superimposed gear. The term shaft should thus be understood functionally, whereby this either means the individual elements of the planetary wheel—sun wheel, hollow wheel or spacer—or the elements coupled with them in a torque-transmitting manner, e.g. in the form of shafts or hollow shafts. The individual shafts thereby take on the function of inputs and outputs depending on the operating state. Thus, the first superimposed gear for the transfer of power from the box input shaft to the box output shaft via the continuously variable transmission comprises an input and two outputs. The input is thereby formed by the first shaft, while the first output, which is connected at least indirectly with the continuously variable transmission, is formed by the third shaft, and the second output, connected in a torque-transmitting manner with the box output shaft, is formed by the second shaft. The second superimposed gear comprises in this operating state an input and an output, whereby the input is also coupled with the box input shaft and is formed by the first shaft of the second superimposed gear and the output of the second shaft. The third shaft is connected to the continuously variable transmission. Means for changing the gear transmission ratio on the transmission are also provided. One of the two superimposed gears—first or second superimposed gear—thereby has pairs of intermeshing planetary wheels between the sun wheel and the hollow wheel. These are pivoted on the spacer. The pairs of intermeshing planetary wheels are also called double-barreled planetary wheels. Based on the embodiment of one of the second superimposed gears designed as a planetary wheel with pairs of intermeshing planetary wheels, which are also called double-barreled planetary wheels, it is guaranteed for the sub-area of the full operating range that the CVT works with a maximum velocity of circulation, whereby a switch in terms of the gear transmission ratio to the individual disks can also take place at a maximum engine speed, i.e. is possible via zero turning, and thus a change in the direction of rotation is to be realized with the transmission in accordance with the invention in addition to the geared neutral. The double-barreled design has the advantage that, in the case of an increase in the revolution speed caused by this at the input coupled with the continuously variable transmission, in particular the hollow wheel of this planetary wheel, this causes a decrease determined in accordance with the design of the other planetary wheel on the output of the each of the other planetary wheels coupled with the continuously variable transmission, in particular the hollow wheel. However, in accordance with this design, it is not possible to let the continuously variable transmission operate over the full operating range twice with maximum velocity of circulation.